CN110473684B - Preparation method of high-coercivity sintered neodymium-iron-boron magnet - Google Patents
Preparation method of high-coercivity sintered neodymium-iron-boron magnet Download PDFInfo
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- CN110473684B CN110473684B CN201910765776.5A CN201910765776A CN110473684B CN 110473684 B CN110473684 B CN 110473684B CN 201910765776 A CN201910765776 A CN 201910765776A CN 110473684 B CN110473684 B CN 110473684B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
- H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
- H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
- H01F1/047—Alloys characterised by their composition
- H01F1/053—Alloys characterised by their composition containing rare earth metals
- H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
- H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
- H01F1/0571—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes
- H01F1/0575—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together
- H01F1/0577—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together sintered
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
- H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
- H01F41/0253—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets
- H01F41/0293—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets diffusion of rare earth elements, e.g. Tb, Dy or Ho, into permanent magnets
Abstract
The invention discloses a preparation method of a high-coercivity sintered neodymium-iron-boron magnet, and belongs to the field of preparation of permanent magnet materials. The high-coercivity sintered neodymium-iron-boron magnet prepared by the traditional diffusion process has the problems of long diffusion time, large consumption of heavy rare earth for diffusion, high cost and the like. According to the invention, firstly, after the hard alloy balls and the heavy rare earth compound powder are uniformly mixed, the mixed powder is accelerated by adopting high-speed airflow, the surface of the sintered neodymium-iron-boron magnet is impacted, so that an amorphous layer or a microcrack area appears on the surface of the magnet, and then the magnet is tempered, so that the sintered neodymium-iron-boron magnet with high coercivity is prepared. The method reasonably utilizes the grain boundary diffusion mechanism and the grain and grain boundary cracking characteristics of the sintered neodymium iron boron permanent magnet, improves the surface diffusion efficiency, and has the advantages of simple process, short diffusion time, high utilization rate of heavy rare earth and the like.
Description
Technical Field
The invention relates to the field of preparation of permanent magnet materials, in particular to a preparation method of a high-coercivity sintered neodymium-iron-boron magnet.
Background
The neodymium iron boron permanent magnet is widely applied to the fields of electronic equipment, medical instruments and motors due to excellent magnetic performance, and particularly, the sintered neodymium iron boron permanent magnet with ultrahigh intrinsic coercivity is a key base material urgently needed in the fields of wind power generation, high-performance industrial motors, medical equipment and the like.
The conventional process for preparing the sintered Nd-Fe-B magnet with high intrinsic coercivity is usually formed by adding a large amount of heavy rare earth elements Dy, Tb and the like into a formula (Nd, HRE)2Fe14And B, the main phase further improves the magnetic crystal anisotropy of the main phase and greatly improves the intrinsic coercivity of the magnet. But since (Nd, HRE)2Fe14B principal phase is lowAnd the magnetization intensity causes the residual magnetism of the magnet to be greatly reduced, further causes the maximum magnetic energy product to be reduced, causes the excessive and unreasonable use of heavy rare earth resources, and is not beneficial to the green sustainable development of the rare earth industry.
Research shows that the intrinsic coercive force of the magnet can be greatly improved and the remanence is kept basically unchanged on the premise of lower usage amount of the heavy rare earth by coating the surface with the heavy rare earth compound and performing grain boundary diffusion on the magnet. However, the method is low in efficiency, long diffusion time is often needed, heavy rare earth is expensive, the utilization rate of heavy rare earth raw materials is low by using a traditional diffusion process, the consumption of the heavy rare earth raw materials is large, and the manufacturing cost of the high-coercivity sintered neodymium iron boron is increased. Therefore, the method for preparing the sintered neodymium iron boron with high coercivity is significant.
Comprehensive analysis has been carried out on the related researches at present, and the research finds that the increase of the contact area between the heavy rare earth compound and the magnet and the grain boundary phase is helpful for improving the surface grain boundary diffusion efficiency. Therefore, the invention discloses a preparation process which adopts high-speed hard alloy and heavy rare earth compound to impact the surface of a magnet, so that a microcrack region and an amorphous region are formed on the surface of the magnet, the contact area between a diffuser and the magnet is greatly increased, the diffusion efficiency is improved, and the preparation process is feasible and efficient in diffusion. The preparation method of the high intrinsic coercivity sintered neodymium iron boron magnet disclosed by the invention has the advantage of improving the intrinsic coercivity of the magnet through surface grain boundary diffusion, and also has the advantage of further reducing the loss of heavy rare earth.
Disclosure of Invention
The invention aims to solve the problems in the existing sintered neodymium iron boron preparation technology and provides a preparation method of high-coercivity sintered neodymium iron boron.
The method comprises the following steps of mixing heavy rare earth powder with a cobalt-based hard alloy under a protective atmosphere, so that heavy rare earth elements are impacted and diffused into the surface of a magnet, and then carrying out annealing heat treatment to obtain the high-coercivity sintered neodymium-iron-boron.
(1) Preparing an alloy ingot by adopting electric arc melting or induction melting.
(2) And carrying out gas atomization treatment on the alloy cast ingot, wherein the temperature is 1000-1500 ℃, the atomization medium is argon or nitrogen, and the atomization pressure is 0.5-15 MPa, so as to obtain rare earth compound powder.
(3) Uniformly mixing the cobalt-based hard alloy ball and the heavy rare earth compound powder under the condition of nitrogen protection, and then impacting the surface of the sintered neodymium-iron-boron magnet by the cobalt-based hard alloy and the heavy rare earth powder through high-pressure airflow to enable an amorphous layer or a microcrack area to appear on the surface of the magnet, so that the heavy rare earth powder is diffused into the surface layer of the magnet along cracks and amorphous areas, and the dropped ball and powder can be recycled. Spherical cobalt-based hard alloy is used, the diameter of a hard alloy ball is controlled to be 3.0-5.0 um, the particle size of heavy rare earth powder is controlled to be 0.5-1.5 um, the air flow speed is controlled to be 10-30 m/s, the impact time is 10-30 min, and after impact is finished, the depth of an amorphous layer or a microcrack area is controlled to be 0.2-1.0 mm.
(4) After the surface treatment of the sintered neodymium iron boron magnet is finished, the magnet is placed into a quartz tube, primary tempering treatment is carried out in a vacuum state, the tempering temperature is 750-950 ℃, the heat preservation time is 2-20h, and finally, a quenching process is adopted for cooling.
(5) And performing secondary tempering treatment on the sintered neodymium-iron-boron magnet in a vacuum state, wherein the tempering temperature is 420-600 ℃, the heat preservation time is 1-5h, and finally, cooling by adopting a quenching process.
The invention has the following advantages:
the invention reasonably utilizes the cracking characteristics of crystal grains and crystal boundaries of the sintered neodymium iron boron magnet, adopts high-speed powder to impact the surface of the magnet, and enables the surface of the magnet to have microcracks and amorphous areas by setting the powder speed and the particle size, thereby promoting the heavy rare earth compound to be efficiently attached to the surface of the magnet, increasing the diffusion area and the contact efficiency and further improving the diffusion efficiency of the magnet.
Detailed Description
The present invention is further described below.
Example 1
Firstly, preparing an alloy ingot by adopting electric arc melting or induction melting; and (3) carrying out gas atomization on the alloy cast ingot at the temperature of 1000 ℃, wherein the atomization medium is nitrogen, and the atomization air pressure is 15MPa, so as to obtain Tb powder. Uniformly mixing the hard alloy ball and the heavy rare earth compound powder under the condition of nitrogen protection, and accelerating the mixed ball material through high-speed airflow to enable the cobalt-based hard alloy ball and the heavy rare earth compound powder to impact the surface of the sintered neodymium-iron-boron magnet. Wherein the diameter of the hard alloy ball is 3.0 μm, the average grain diameter of the heavy rare earth compound powder is controlled to be 0.5 μm, the shot blasting speed is controlled to be 10m/s, and the impact time is 10 min. And (3) putting the magnet into a quartz tube, carrying out primary tempering treatment in a vacuum state, wherein the tempering temperature is 750 ℃, the heat preservation time is 2 hours, and finally cooling by adopting a quenching process. And performing secondary tempering treatment on the magnet in a vacuum state, wherein the tempering temperature is 420 ℃, the heat preservation time is 1h, and finally, cooling by adopting a quenching process.
Example 2
Firstly, preparing an alloy ingot by adopting electric arc melting or induction melting; and (3) carrying out gas atomization on the alloy cast ingot at the temperature of 1200 ℃, wherein the atomization medium is argon or nitrogen, and the atomization air pressure is 10MPa, so as to obtain Tb powder. Under the condition of nitrogen protection, after the hard alloy ball and the heavy rare earth compound powder are uniformly mixed, the mixed ball material is accelerated through high-speed airflow, so that the cobalt-based hard alloy ball and the heavy rare earth compound powder impact the surface of the sintered neodymium-iron-boron magnet. Wherein the diameter of the hard alloy ball is 4.0 μm, the average grain diameter of the heavy rare earth compound powder is controlled to be 1.0 μm, the shot blasting speed is controlled to be 20m/s, and the impact time is 20 min. And (3) putting the magnet into a quartz tube, carrying out primary tempering treatment in a vacuum state, wherein the tempering temperature is 850 ℃, the heat preservation time is 11 hours, and finally cooling by adopting a quenching process. And performing secondary tempering treatment on the magnet in a vacuum state, wherein the tempering temperature is 500 ℃, the heat preservation time is 3 hours, and finally cooling by adopting a quenching process.
Example 3
Firstly, preparing an alloy ingot by adopting electric arc melting or induction melting; and (3) carrying out gas atomization on the alloy cast ingot at the temperature of 1000 ℃, wherein the atomization medium is argon or nitrogen, and the atomization pressure is 5MPa to obtain Tb powder. Under the condition of nitrogen protection, the original sintered neodymium-iron-boron magnet is uniformly mixed with the hard alloy ball and the heavy rare earth compound powder, and then the mixed ball material is accelerated through high-speed airflow, so that the cobalt-based hard alloy ball and the heavy rare earth compound powder impact the surface of the sintered neodymium-iron-boron magnet. Wherein the diameter of the hard alloy ball is 5.0 μm, the average grain diameter of the heavy rare earth powder is controlled to be 1.5 μm, the shot blasting speed is controlled to be 30m/s, and the impact time is 30 min. The magnet is placed in a quartz tube, primary tempering treatment is carried out in a vacuum state, the tempering temperature is 950 ℃, the heat preservation time is 20 hours, and finally a quenching process is adopted for cooling. And performing secondary tempering treatment on the magnet in a vacuum state, wherein the tempering temperature is 600 ℃, the heat preservation time is 5 hours, and finally cooling by adopting a quenching process.
Comparative example 1
Coating Tb powder on the surface of a sintered neodymium-iron-boron magnet under the protection of nitrogen atmosphere, placing the magnet into a quartz tube, carrying out primary tempering treatment under a vacuum state, wherein the tempering temperature is 750 ℃, the heat preservation time is 2 hours, and finally cooling by adopting a quenching process. And performing secondary tempering treatment on the magnet in a vacuum state, wherein the tempering temperature is 420 ℃, the heat preservation time is 1h, and finally, cooling by adopting a quenching process.
Comparative example 2
Coating heavy Tb powder on the surface of a sintered Nd-Fe-B magnet under the protection of nitrogen atmosphere, placing the magnet into a quartz tube, placing the magnet into the quartz tube, carrying out primary tempering treatment under a vacuum state, wherein the tempering temperature is 850 ℃, the heat preservation time is 11 hours, and finally cooling by adopting a quenching process. And performing secondary tempering treatment on the magnet in a vacuum state, wherein the tempering temperature is 500 ℃, the heat preservation time is 3 hours, and finally cooling by adopting a quenching process.
Comparative example 3
Coating heavy Tb powder on the surface of a sintered Nd-Fe-B magnet under the protection of nitrogen atmosphere, placing the magnet into a quartz tube, carrying out primary tempering treatment under a vacuum state, wherein the tempering temperature is 950 ℃, the heat preservation time is 20 hours, and finally cooling by adopting a quenching process. And performing secondary tempering treatment on the magnet in a vacuum state, wherein the tempering temperature is 600 ℃, the heat preservation time is 5 hours, and finally cooling by adopting a quenching process.
Table 1 shows intrinsic coercive force of the sintered nd-fe-b magnet of each example and comparative example.
| Numbering | Categories | Intrinsic coercivity (kOe) |
| 1 | Example 1 | 18.7 |
| 2 | Example 2 | 22.9 |
| 3 | Example 3 | 21.8 |
| 4 | Comparative example 1 | 14.6 |
| 5 | Comparative example 2 | 20.2 |
| 6 | Comparative example 3 | 19.6 |
| 7 | Initial magnet | 12.1 |
TABLE 1
The present invention is further illustrated by the following examples, which are intended to facilitate the understanding of the reader, but are not intended to limit the scope of the present invention to such examples, and any technical extensions or remnants of the present invention may be protected by the present invention.
Claims (3)
1. A preparation method of high-coercivity sintered neodymium iron boron is characterized by comprising the following steps:
(1) preparing an alloy ingot by adopting electric arc melting or induction melting;
(2) carrying out gas atomization treatment on the alloy cast ingot, wherein the temperature is 1000-1500 ℃, the atomization medium is argon or nitrogen, and the atomization pressure is 0.5-15 MPa, so as to obtain heavy rare earth metal or alloy powder;
(3) uniformly mixing the cobalt-based hard alloy ball and the heavy rare earth metal or alloy powder under a protective atmosphere, wherein the diameter of the cobalt-based hard alloy ball is 3.0-5.0 mu m, the particle size of the heavy rare earth metal or alloy powder is 0.5-1.5 mu m, and N is used2Accelerating the mixture of the cobalt-based hard alloy ball and the heavy rare earth metal or alloy powder to 10-30 m/s by high-speed airflow, impacting and sintering the surface of the neodymium-iron-boron magnet, controlling the impacting time to be 10-30 min, enabling the surface of the magnet to have an amorphous layer or a microcrack area, controlling the depth of the amorphous layer or the microcrack area to be 0.2-1.0 mm, and then tempering the magnet.
2. The method for preparing the high-coercivity sintered neodymium-iron-boron according to claim 1, wherein the method comprises the following steps: the tempering process comprises the following steps:
1) putting the magnet into a quartz tube, carrying out primary tempering treatment under a vacuum state, wherein the tempering temperature is 750-950 ℃, the heat preservation time is 2-20h, and then quenching;
2) performing secondary tempering treatment on the magnet treated in the step 1) in vacuum, wherein the tempering temperature is 420-600 ℃, the heat preservation time is 1-5h, and finally quenching to room temperature.
3. The method for preparing the high-coercivity sintered neodymium-iron-boron according to claim 1, wherein the method comprises the following steps: the expression of the heavy rare earth metal or the alloy is RE1-xTMxWherein x is more than or equal to 0 and less than or equal to 0.5, RE is one or more of Dy, Tb, Er, Gd and Lu, and TM is one or more of Cu, Co, Ga, Al, V, Nb, Ti and Zr.
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| CN113421764B (en) * | 2021-07-02 | 2023-06-09 | 中国计量大学 | Preparation method of high-toughness and high-coercivity permanent magnet |
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